The mechanism of permeation across artificial bilayers have been sorted out in the minutest detail and the time is ripe to apply the ideas and approaches to biological membranes. The question whether a particular transport system exhibits "carrier" or "channel" characteristics provides a framework and a set of experimental approaches to study permeability mechanisms. Several pertinent questions ought to be dealt with: How the chemical energy release, for example, from the hydrolysis to ATP is transferred to the ion per se; How the voltage regulates the opening and closing of "channels" in nerve membranes; what is the molecular nature of "carriers" and "channels" in biological membranes and what are the regulatory factors - ionic or otherwise - controlling ion transport. Finally, the discussion of some of these topics and questions - no conference could possibly cover all of them - may provide a stimulus for new developments. The field in question, at this time, is a lively one and on the brink of a major breakthrough. The conference, hopefully, will facilitate such a breakthrough and help put it in a wider perspective in the overall biological problems.